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A computational and theoretical investigation of acoustical and vibrational properties of rigid thin fiberglass material was carried out for different boundary conditions. Fiberglass materials could be applied in industries varying from the aircraft and automotive sectors to the built environment and construction sectors. Plate vibration and acoustic radiation were applied to predict the deflection of the thin fiberglass material and sound radiation efficiency at different locations on its surface, while a study-controlled equation of motion known as the Kirchhoff thin plate theory was applied for a COMSOL simulation of the thin material to determine the deflection of the plate and to obtain stress distribution, velocity contour, displacement, and acoustic pressure at the first resonance of the material. The results of this paper show that thin fiberglass material could be applied to sandwich building elements to form panels for reducing airborne noise and to lessen the sound transmission of structural borne noise, to cover noise barriers to make them more sustainable and weather resistant, to dampen the vibration of machines, and to reduce the structural vibration of buildings. [ABSTRACT FROM AUTHOR]

A computational and theoretical investigation of acoustical and vibrational properties of rigid thin fiberglass material was carried out for different boundary conditions. Fiberglass materials could be applied in industries varying from the aircraft and automotive sectors to the built environment and construction sectors. Plate vibration and acoustic radiation were applied to predict the deflection of the thin fiberglass material and sound radiation efficiency at different locations on its surface, while a study-controlled equation of motion known as the Kirchhoff thin plate theory was applied for a COMSOL simulation of the thin material to determine the deflection of the plate and to obtain stress distribution, velocity contour, displacement, and acoustic pressure at the first resonance of the material. The results of this paper show that thin fiberglass material could be applied to sandwich building elements to form panels for reducing airborne noise and to lessen the sound transmission of structural borne noise, to cover noise barriers to make them more sustainable and weather resistant, to dampen the vibration of machines, and to reduce the structural vibration of buildings.

Male crickets attract females by producing calls with their forewings. Louder calls travel further and are more effective at attracting mates. However, crickets are much smaller than the wavelength of their call, and this limits their power output. A small group called tree crickets make acoustic tools called baffles which reduce acoustic short-circuiting, a source of dipole inefficiency. Here, we ask why baffling is uncommon among crickets. We hypothesize that baffling may be rare because like other tools they offer insufficient advantage for most species. To test this, we modelled the calling efficiencies of crickets within the full space of possible natural wing sizes and call frequencies, in multiple acoustic environments. We then generated efficiency landscapes, within which we plotted 112 cricket species across 7 phylogenetic clades. We found that all sampled crickets, in all conditions, could gain efficiency from tool use. Surprisingly, we also found that calling from the ground significantly increased efficiency, with or without a baffle, by as much as an order of magnitude. We found that the ground provides some reduction of acoustic short-circuiting but also halves the air volume within which sound is radiated. It simultaneously reflects sound upwards, allowing recapture of a significant amount of acoustic energy through constructive interference. Thus, using the ground as a reflective baffle is an effective strategy for increasing calling efficiency. Indeed, theory suggests that this increase in efficiency is accessible not just to crickets but to all acoustically communicating animals whether they are dipole or monopole sound sources. [ABSTRACT FROM AUTHOR]

Cross-Laminated Timber (CLT) is a building technology that is becoming increasingly popular due to its sustainable and eco-friendly nature, as well as its availability. Nevertheless, CLT presents some challenges, especially in terms of impact noise and airborne sound insulation. For this reason, many studies focus on the vibro-acoustic behavior of CLT building elements, to understand their performance, advantages and limitations. In this paper, a 200 mm CLT floor has been characterized in the laboratory, according to ISO standards, by three noise sources: dodecahedron, standard tapping machine and rubber ball. In order to understand the vibro-acoustic behavior of the CLT floor, measurements through the analysis of sound pressure levels and velocity levels, measured by dedicated sensors, were performed. Analysis was carried out in order to understand what is prescribed by the prediction methods available in the literature and by the simulation software. Then, a specific prediction law for the CLT floor under investigation was derived. Finally, an analysis on sound radiation index is provided to complete the vibro-acoustic study. [ABSTRACT FROM AUTHOR]

• Investigation into influences of temperature effects on the structure-borne noise of track–bridge. • The adopted method is suitable for exhibiting changes in track irregularity, structural frequency response, and sound radiation efficiency. • Variations in track irregularity and structural frequency response should not be disregarded. • Temperature effects have a minor impact on the system's sound radiation efficiency. In recent years, concerns have arisen regarding the periodic deformation of high-speed railway tracks owing to the temperature effects caused by the solar radiation. This phenomenon has prompted investigations into temperature-induced changes in the dynamic responses of vehicle–track–bridge systems. Previous studies have commonly taken the additional track irregularity caused by thermal deformation as the sole factor affecting dynamic responses while neglected changes in the structural frequency response characteristics. Structural radiation noise is also a prominent issue that affects the lives of people and the environment. However, studies on track–bridge-borne noise rarely consider the influence of temperature. To address the impact of temperature on structure-borne noise radiated by tracks and bridges, this study employed a sequentially coupled multi-physics analysis method. This approach allowed a comprehensive exploration of the temperature effects on track irregularities, structural frequency responses, and sound radiation efficiency. A full-scale temperature deformation field test of a CRTS III slab was also conducted to determine the necessary initial thermodynamic boundary conditions. The analysis results revealed that the thermally induced deterioration of track irregularity and changes in structural frequency response characteristics were the primary factors affecting structure-borne noise radiated by track–bridges under local climate conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Cross-Laminated Timber (CLT) is a building technology that is becoming increasingly popular due to its sustainable and eco-friendly nature, as well as its availability. Nevertheless, CLT presents some challenges, especially in terms of impact noise and airborne sound insulation. For this reason, many studies focus on the vibro-acoustic behavior of CLT building elements, to understand their performance, advantages and limitations. In this paper, a 200 mm CLT floor has been characterized in the laboratory, according to ISO standards, by three noise sources: dodecahedron, standard tapping machine and rubber ball. In order to understand the vibro-acoustic behavior of the CLT floor, measurements through the analysis of sound pressure levels and velocity levels, measured by dedicated sensors, were performed. Analysis was carried out in order to understand what is prescribed by the prediction methods available in the literature and by the simulation software. Then, a specific prediction law for the CLT floor under investigation was derived. Finally, an analysis on sound radiation index is provided to complete the vibro-acoustic study.

Cymbals are percussion instruments that vibrate and radiate sounds when hit with a stick. A bell is the raised section in the middle of the cymbal and its size produces different sounds. In this study, we investigate the effect of bell size on the sound characteristics of cymbals. The radiated sounds and vibrations for cymbals with two different bell sizes are measured. In addition, the natural frequency and mode shape are obtained by finite element analysis and the sound radiation efficiency is calculated for each mode. The measured results indicate that the sound frequency characteristics for the large bell show three peaks with large sound pressure within the range of 1000 to 3000 Hz and the sound pressure for the small bell is larger than that for the large bell within the range of 4000 to 5000 Hz. The vibration frequency characteristics show there is no remarkable difference between the large and small bells. The sound radiation efficiencies indicate that the large bell has many modes with high radiation efficiency within the range of 1000 to 3000 Hz and their modes have a small number of nodal diameters and a large deformation at the bell. The small bell has many modes with high efficiency within the range of 4000 to 5000 Hz. This is reason for the difference in sound characteristics between the large and small bells.

Sound radiation of thin plates is a common problem in engineering. Hashimoto proposed the discrete calculation method (DCM) to deal with the problem. The calculation of the radiation impedance of the rectangular element is more cumbersome than that of the circular one, so the discrete rectangular radiation element is approximated by the circular one. However, error is also introduced. The formula developed by Sha has been employed to get self- and mutual-radiation impedances of rectangular radiation element. Numerical study was performed to verify error introduced by the approximation Hashimoto adopted. Experimental researches on sound radiation of a 2mm-thick and a 4mm-thick magnesium alloy plates were also carried out to evaluate the errors introduced by the approximation. The experimental results indicate that the circular approximation Hashimoto adopted overestimates the sound radiation efficiency. The maximum error levels of the radiation efficiencies of the 2mm-thick and 4mm-thick magnesium alloy plates are up to 0.15 and 0.12, respectively. The effect of element aspect ratio on the sound radiation efficiency is also remarkable. [ABSTRACT FROM AUTHOR]

This paper deals with the problem of the effect of discretization level and certain other parameters characterizing the measurement setup on accuracy of the process of determination of the sound radiation efficiency by means of the Discrete Calculation Method (DCM) described by Hashimoto (2001). The idea behind DCM consists in virtual division of an examined sound radiating structure into rectangular elements each of which is further assumed to contribute to the total radiation effect in the same way as a rigid circular piston having the surface area equal to this of the corresponding virtual element and vibrating in an infinite rigid baffle. The advantage of the method over conventional sound radiation efficiency measurement techniques consists in the fact that instead of acoustic pressure values, source (plate) vibration velocity amplitude values are measured in a selected number of regularly distributed points. In many cases, this allows to determine the sound radiation efficiency with sufficient accuracy, especially for the low frequency regime. The key part of the paper is an analysis of the effect of discretization level (i.e. the choice of the number of points at which vibration amplitude measurements are to be taken with the use of accelerometers) on results obtained with the use of the method and their accuracy. The problem of determining an optimum level of discretization for given excitation frequency range is a very important issue as the labor intensity (time-consuming aspect) of the method is one of its main flaws. As far as the technical aspect of the method is concerned, two different geometrical configurations of the measurement setup were tested. [ABSTRACT FROM AUTHOR]

Underwater radiated noise is one of the most important performances related to the stealth of a naval vessel. However, the evaluation frequently cannot be performed due to the problem of the test expense. The specification of the hull vibration is an effective method used to specify the underwater radiated noise indirectly. Therefore, in order to specify hull vibration, the sound radiation efficiency should be correctly determined. In this paper, the sound radiation efficiency which was modified with experimentally derived sound radiation efficiency as well as Maidanik's and Uchida's sound radiation efficiency is suggested and verified through experiments. Based on the determined sound radiation efficiency in this research, the specification of the hull vibration to satisfy with the limit of the underwater radiated noise is suggested for a ship. [ABSTRACT FROM AUTHOR]

In this study, the sound radiation characteristics of the laminated structures reinforced by honeycomb and composed by viscoelastic material was investigated. Temperature- and frequency-dependent behaviors of the viscoelastic material were considered in this analysis, those parameters affected the dynamics effective properties of the composite structure. After the dynamic equivalent effective stiffness and the dynamic deformation of the structure are determined according to the homogenous asymptotic method, the sound radiation behaviors of the structures in fields of frequency and temperature are achieved. Consequently, the sound radiation characteristic, such as the sound pressure in far-field and the sound radiation efficiency that influenced by the geometry dimensions of the honeycomb structure was examined. Finally, the study is validated by the degeneration method with a degeneration mathematical model that performed in the published literature. [ABSTRACT FROM AUTHOR]